Marine Bio - Chapter 7

Common characteristics shared by all animals

All animals are eukaryotic and multicellular and heterotrophic. They lack a backbone (invertebrates), and some have specialized tissues organized into organs

Sponge structures and their functions

Collar cells (choanocytes) create water currents and capture food particles, not support. The osculum is the opening through which water leaves the sponge. Pore cells (porocytes) let water enter, spongin provides flexible support fibers, and gametes are used for reproduction

A feature shared by all sponges

All sponges are multicellular organisms. They are not all marine (some live in fresh water), they produce both sexually and asexually, and they lack specialized circulatory organs

Food source of sponges and all filter feeds

Filter feeders consume all particulate matter suspended in the water column. This includes plankton, organic debris, and other small particles carried by water currents, rather than only bottom deposits or particular prey types

Larval stage

A larva is an early, immature stage of development of an organism that differs in form from the adult. It is typically part of the plankton and must undergo metamorphosis to reach the adult form. It is not yet able to reproduce.

Features shared by all cnidarians

All cnidarians have nematocysts (stinging cells), are multicellular, and show radial symmetry. They lives in both marine and freshwater environments. They have an incomplete digestive tract with only a single open (mouth, not a complete tract with separate mouth and anus

Anthozoan

Reef corals are anthozoans, the class of cnidarians that includes corals and sea anemones. The portuguese Man-of-War, colonial hydroids, sea nettle jellyfish, and sea wasps belong to cnidarians classes

Most common feeding mode of cnidarians

Most cnidarians are carnivores. They use their tentacles and stinging nematocysts to capture and immobilize live prey such as small fish and zooplankton

Body form of free-floating cnidarians like jellyfish

Free-floating cnidarians like jellyfish have a medusa form. This is the bell-shaped, swimming body form, in contrast to the sessile polyp form anchored to the bottom

Distinguishing feature of comb jellies

eight bands of cilia (combs) used for locomotions. they are radially symmetrical (not bilateral) and capture prey with sticky colloblast cells rather than nemtocysts

Correct pairing of body surfaces in bilaterally symmetrical animal

The ventral surface is the lower or belly surface, not the brain. The dorsal surface is the upper surface, the anterior surface is head end, and the posterior surface is the rear end

Bilateral symmetry

Led to cephalization - the concentration of sensory organs and a brain at the anterior (head) end. This drove the evolution of a more complex nervous system in invertebrates

Classification of comb jellies

as the phylum Ctenophora. distinct from cnidarians, flatworms (Platyhelminthes), and sipunculans

Characterisitcs of flatworms

have a central nervous system. They show bilateral symmetry, lack nematocysts, and have an incomplete digestive tract ( a single opening) rather than a complete one

Flukes (trematodes)

a group of parasitic flatworms that infect fishes, seabirds, and other marine animals. they are not free-living like turbellarians

distinctive feature of ribbon worms

their long, eversible proboscis. this structure is used to capture prey and is housed in a fluid-filled cavity called the rhynochocoel

Correct phylum-to-animals pairings

Beard worms belong to phylum Annelida, not platyhelminthes. comb jellies are phylum ctenophora, roundworms are phylum Nematoda ribbon worms are phylum Nemertea, and sponges are phylum porifera

Polychaete worm

an Annelida (segmented worm) a class of annelids character by many bristles (chaetae) on each segment

Deposit-feeding animals

they feed on organic matter that settles on the bottom. They ingest sediment and extract the organic particles it contains, unlike suspension feeders that capture particles from the water

A feature of polychaete worms

they show segmentation - their bodies are divided into repeating segments. they have bilateral symmetry and a complete digestive tract, not a mantle ( that is a mollusc feature)

Beard worms (pogonophorans)

they lack a digestive tract, They have no mouth or gut and instead obtain nutrition through symbiotic bacteria housed in a specialized organ.

Arrow worms (chaetognaths)

active predators that feed on live prey, capturing small organisms such as copepods and fish larvae with grasping spines near their mouths

Nudibranch (sea slug)

a type of mollusc belonging to the class Gastropoda and is a marine Gastropoda that has lost its shell in adulthood

Feature shared by all molluscs

All molluscs have a soft body covered by a mantle. The mantle may secrete a shell, and molluscs typically have a foot, visceral mass, and often a radula

Mollusc class pairings

Mussels belong to class Bivalvia, not Gastropoda. Oysters are bivalves, chitons are polplacophorans, and octopus are cephalopods

Radula and crystalline

Part of the digestive system of mulluscs. The radula is a rasping tongue like structure for scraping food and the crystakkine style secretes enzymes to help digest food

arthropods

copepods, krill, barnacles, and blue crabs are all arthropods (crustaceans). They have jointed legs and a segmented body and a chitinous exoskeleton, but the jointed appendages are their defining feature

Crustaceans

copepods, barnacles, shrimps, and beach hoppers are all crustaceans

echinoderms

they have a water vascular system, their network of water-filled canals powering their tube feet for movement, feeding, and gas exchange

echinoderm class pairings

sea stars are asteroidea, sea cucumbers are holothuroidea, and brittle stars are ophiuroidea

Molting (ecdysis)

crustaceans shed their exoskeletons periodically to grow a new, larger one to accommodate growth

Siphon (funnel)

a muscular tube that expels water forcefully to propel the animal through the water by jet propulsion. cephalopods have a siphon.

zoea larva

an early larval stage of many crustaceans, including crabs, characterized by spiny carapace and appendages used for swimming. a crab has a zoea larval form

organism most highly evolved

a lancelet is the most highly evolved, lancelets are chordates (like vertebrates), possessing a notochord, making them more closely related to and more advanced than tunicates, sea urchins, and crinoids

Bryozoan colonies

consist of tiny zooids that secrete skeletons of a wide variety of shapes. these small colonial animals are common encrusting organisms in marine environments

lamp shells known only as fossils

As many as 30,000 species of lamp shells (brachiopods) are known only as fossils. Brachiopods were far more diverse in the past than they are today

Lophophorates

Lamp shells (brachiopods) and phoronids are lophophorates. These animals possess a lophophore, a crown of ciliated tentacles used for feeding. Barnacles and horseshoe crabs are arthropods, not lophophorates.

Nematodes as mutualists

Nematodes are often mutualists, living in beneficial associations with other organisms. In such relationships, both the nematode and its host benefit, such as nematodes that help break down organic matter in the host's environment.